In U.S. Pat. Nos. 4,758,156 to Johnson, 4,894,011 to Johnson, and 5,118,297 to Johnson, there are described devices or tools for applying filler material, such as gutta percha or the like, to an endodontically prepared root canal of a tooth of a patient. The devices disclosed in these patents generally comprise a filler member or body, also referred to as obturator, in the form of an elongated shaft having a proximal handle portion. The proximal and distal portions of the obturator are severed or broken apart after the obturator is placed into the root canal so as to leave the distal portion in the canal.
In the first two patents mentioned above, the severing or breaking of the body portion of the obturator is made manually at a preformed, weakened point in the body. This approach is not practical because of the very high risk of prematurely breaking the obturator at the weakened point when inserting the obturator into a curved root canal. Further, because the weakened point is predetermined, the dentist has no discretion in choosing the length of the remaining distal portion of the obturator.
In the third patent mentioned above, U.S. Pat. No. 5,118,297, severing of the body must be carried out by use of either a heating instrument or a burr, and this also has drawbacks given the limited space in the root canal and pulpal chamber in which the dentist has to work.
A further device of this type is disclosed in U.S. Pat. No. 5,588,835 to Kert. This device includes a central filler body which surrounds an insulation rod, and the latter is withdrawn after insertion, leaving the filler body in the canal. However, the filler body in the canal still must be trimmed after withdrawal of the central insertion rod.